Stochastic Models and their Deterministic Limits

In the previous chapters, we have used deterministic models to derive congestion control schemes and AQM schemes that are fair and achieve high utilization. However, in the real Internet, there are many sources of randomness: unresponsive flows which do not respond to congestion indication,the probabilistic nature of packet marking by an AQM scheme,asynchronous updates among sources,the inability to precisely model window flow control mechanism, andthe initial ramp-up phase (for example, slow start in TCP flow control) of the congestion control mechanism.